Mexican Chiton, Onchidella binneyi

Mexican Chiton, Onchidella binneyi. Chiton collected off a rock above the water line at Km 21, Cabo Real, Baja California Sur, April 2007. A unique collection made mid-morning as they were out in plain sight, moving fairly rapidly back to shelter, which was about 10 meters away. Size: 2.5 cm (1.0 inch). Identification courtesy of Dr. Richard Brusca, Tucson, Arizona.

The Mexican Chiton, Onchidella binneyi, is a member of the Onchidiidae Family of False Chitons, that is a small air breathing sea slug that are found in the intertidal zone just above the water line confined to the crack and crevices within large boulders on rocky coasts. They are shell-less very exceptional marine oulmonate (have lungs versus gills) gastropod mollusks and therefore more closely related to air-breathing land and freshwater snails and slugs than they are to most other sea snails and sea slugs. They are charcoal gray with a long narrow foot and reach a maximum length of just over 2.5 cm (1.0 inch). They feed at night and are rarely seen in the direct sunlight. The exact range of the Mexican Chiton is unknown except they have been documented in the northern Sea of Cortez and now at the tip of the Baja. They are the most common Chiton found in Mexican waters.